Components in power generation systems, such as the turbine rotor blades and the turbine stator blades, are used in turbine equipment and can be exposed to an erosive environment, resulting in erosion caused by water droplets, for example, in steam and/or by fine dust from oxide scale. In particular, water droplets can cause erosion of rear-stage turbine blades, where such water droplets are mixed with the steam for turbine driving. Erosion of turbine blades is problematic because it results in blade thinning and fatigue breakdown of the blade brought about by erosion.
Various erosion preventative measures have been implemented to try to increase the durability of turbine components against erosion. One of these preventative measures involves methods that use low heat-input build-up welding with a high energy-density heat source, such as laser beams to build up a plurality of single layers on the turbine component.
Known build-up welding techniques take a significant amount of time to produce the desired erosion protection layer. Another problem with using such build-up techniques is that the erosion layer must also be machined after formation to the desired blade geometry, increasing processing steps and time in manufacturing, thereby increasing costs.
Some build-up welding techniques use STELLITE®, a cobalt-chromium alloy available from Deloro Stellite Holdings Corporation of Goshen, Ind. Use of STELLITE® can cause several undesirable features, such as, forming a complex carbon dilution layer, creating issues for welding operations, causing cracking under high-temperatures along build-up welded portions, creating a need for significant machining to get to a desired component size/geometry, or combinations thereof.
Another preventative measure is to use an erosion shield, for example, including STELLITE®. The erosion shield is secured to the turbine component and protects the component from erosion. Materials for such erosion shields are provided in wrought condition, requiring processing and/or machining to achieve desired sizes and/or geometries. Such processing and/or machining is especially expensive for complex shapes, such as turbine blades or airfoils.
A process of producing or fabricating a shield, a process of preparing a component, and an erosion shield that do not suffer from one or more of the above drawbacks would be desirable in the art.